Extensive literature is available on the characteristics of the hemoglobin molecule and of its isolated subunits. The conformation of the protein in the crystal form and in solution, its acid base behavior, viscosity, diffusion, sedimentation behavior, optical activity and immunological properties have been investigated in great detail. It appears that all of these characteristics are function of the structure of the polypeptide chains, and of their interaction with the heme and with the partner subunits in the native molecule. It is expected that even large fragments of hemoglobin subunits will have less ordered structure that in the intact molecule. Therefore, new physico- chemical and immunological properties will appear in the fragments. These will show the physico-chemical relevance of the folding of the hemoglobin molecule and provide the parameters necessary to follow the reconstitution of the original structure in the fragments. The local structural importance of amino acid substitutions in mutant hemoglobins might be detected investigating the behavior of peptides obtained from mutant hemoglobins. Using subunit fragments antibodies specific for special sites can be obtained and used as diagnostic tools,and to better investigate the conformation in solution of these proteins.